On Tue, Dec 14, 2021 at 1:07 PM Dilip Kumar <dilipbal...@gmail.com> wrote: > > On Tue, Dec 14, 2021 at 8:20 AM Amit Kapila <amit.kapil...@gmail.com> wrote: > > > > On Mon, Dec 13, 2021 at 6:55 PM Masahiko Sawada <sawada.m...@gmail.com> > > wrote: > > > > In streaming cases, we don’t know when stream-commit or stream-abort > > > comes and another conflict could occur on the subscription in the > > > meanwhile. But given that (we expect) this feature is used after the > > > apply worker enters into an error loop, this is unlikely to happen in > > > practice unless the user sets the wrong XID. Similarly, in 2PC cases, > > > we don’t know when commit-prepared or rollback-prepared comes and > > > another conflict could occur in the meanwhile. But this could occur in > > > practice even if the user specified the correct XID. Therefore, if we > > > disallow to change skip_xid until the subscriber receives > > > commit-prepared or rollback-prepared, we cannot skip the second > > > transaction that conflicts with data on the subscriber. > > > > > > > I agree with this theory. Can we reflect this in comments so that in > > the future we know why we didn't pursue this direction? > > I might be missing something here, but for streaming, transaction > users can decide whether they wants to skip or not only once we start > applying no? I mean only once we start applying the changes we can > get some errors and by that time we must be having all the changes for > the transaction. >
That is right and as per my understanding, the patch is trying to accomplish the same. > So I do not understand the point we are trying to > discuss here? > The point is that whether we can skip the changes while streaming itself like when we get the changes and write to a stream file. Now, it is possible that streams from multiple transactions can be interleaved and users can change the skip_xid in between. It is not that we can't handle this but that would require a more complex design and it doesn't seem worth it because we can anyway skip the changes while applying as you mentioned in the previous paragraph. -- With Regards, Amit Kapila.
